All I know is wdg-html-validator_1.6.2-8_all.deb is now obsolete.
So the user does # apt-cache search validator.*HTML5 libhtml5parser-java - validator.nu HTML parser implementation in Java libhtml5parser-java-doc - Documentation for libhtml5parser-java Voila! But alas he installs the packages only to find there is no way / instructions to do his familiar $ validate file.html line 335 column 1 - Warning: missing </a> before </p> So he doesn't know why he downloaded the package.